"""n=1
while n<=10:
    print(n)
    n=n+1"""
a=-1
b=-1
p=0
print("Euklid-NSD")
while (a<0 or b<0):
    if p>0:
        print("a,b nesmú byť záporné!")
    p=p+1

    while True:
        a=input("Zadaj a:")
        b=input("Zadaj b:")
        try:
            a=int(a)
            b=int(b)
            break
        except ValueError:
            print("Ešte raz....")
       

while (a!=0):
    if a>=b:
        a=a-b
    else:
        a,b=b,a
print("NSD je ",b,".")